The present invention relates generally to dimming control for lighting devices. More particularly, the present invention relates to a power line communication system for transmitting a dimming level to an electronic ballast or LED driver that regulates output current to an associated lighting device.
Power line communication systems are known in the art for communicating a dimming level to a lighting circuit such as an electronic ballast or LED driver over an AC power line. The dimming level determines the power output of the lighting circuit and therefore the lighting intensity of an associated lighting device such as a fluorescent lamp or LED array. A power line controller is operable to generate a dimming control signal and to insert that signal on the AC power signal being transmitted over the AC power line to a power line receiver associated with the lighting circuit. The power line receiver then extracts this information from the AC power signal and generates a dimming level signal corresponding to the desired dimming level, which then causes the lighting circuit to generate an output signal to the lighting device in accordance with the desired dimming level. In this manner, a user can control the power consumed by the lighting device and accordingly a lighting intensity.
Several prior art solutions exist for transmitting information to a lighting circuit such as an electronic ballast over AC power lines, including using power line modems, high frequency injection codes and line voltage modulation codes. Unfortunately, the equipment required to insert information into the AC power signal and then extract the information at the lighting circuit is expensive. Furthermore, these systems are particularly sensitive to noise and require control signals with high signal levels to communicate the desired dimming level over the power line. This is particularly true if the system is communicating with several lighting circuits at once.
What is needed, then, is a power line communication system that inserts information on the AC power signal that is more cost efficient and less sensitive to noise.